Pathogenesis of membranous nephropathy: recent advances and future challenges

Potential Modulatory Effects of Hesperidin on the JAK/STAT Pathway in Mesangial Proliferative Glomerulonephritis

Mesangial proliferative glomerulonephritis (MsPGN) is a common type of glomerular disease characterized by immune complex deposition and inflammation in the kidney, leading to renal dysfunction. Currently, treatment options for MsPGN are limited, and there is a need for effective therapeutic interventions. Hesperidin (HSP), a natural flavonoid glycoside, has shown promising anti-inflammatory and antioxidant properties in various disease models. This study aimed to investigate the therapeutic potential of HSP for MsPGN and explore its possible mechanism of action. A male Wistar rat model of MsPGN was established via tail vein injection of Thy-1 monoclonal antibody, and the rats were divided into four groups: Control, MsPGN, MsPGN + HSP, and MsPGN + Prednisone. After 7 days of intervention, the therapeutic effects of HSP were evaluated through biochemical and histological analyses. Our results demonstrated that HSP treatment significantly reduced the levels of blood urea nitrogen, serum creatinine, total cholesterol, and triglycerides, and improved renal pathology. Additionally, pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-2, and monocyte chemoattractant protein-1, were markedly decreased. Immunofluorescence analysis revealed reduced levels of immunoglobulin G and C5b-9, along with decreased immune complex deposition in the kidneys. Furthermore, HSP downregulated the phosphorylation levels of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), suggesting modulation of the JAK/STAT pathway. In conclusion, HSP might effectively alleviate renal injury, reduce renal inflammatory response, and inhibit renal immune complex deposition, potentially through the suppression of the JAK/STAT pathway.

Shen-Qi-Di-Huang Decoction induces autophagy in podocytes to ameliorate membranous nephropathy by suppressing USP14

ETHNOPHARMACOLOGICAL RELEVANCE

Shen-Qi-Di-Huang decoction (SQDHD) is a renowned decoction in traditional Chinese medicine, dating back to the Qing Dynasty. SQDHD has been widely applied in treating renal diseases, including Membranous nephropathy (MN), with its proven positive clinical outcomes. Nevertheless, the precise mechanism by which SQDHD exerts its therapeutic effects on MN remains uncertain.

AIM OF THE STUDY

The present research aimed to observe whether SQDHD promotes podocyte autophagy by inhibiting USP14 to increase the K63 ubiquitination of Beclin1, thereby improving MN.

MATERIALS AND METHODS

An MN model was established in rats using Passive Heyman Nephritis (PHN) to explore the underlying mechanisms in vivo. The kidney function parameters were evaluated, and the histomorphology of glomerular tissues was examined. Autophagy-related protein expression was assessed using immunofluorescence staining and western blotting assays. Co-immunoprecipitation (Co-IP) was used to detect the K63 ubiquitination of Beclin1. MPC5 cells were treated in vitro with serum obtained from several rat groups. Subsequently, the expression of autophagy-related proteins, formation of autophagosomes, expression of USP14, and K63 ubiquitination of Beclin1 were quantified.

RESULTS

Our results demonstrated that SQDHD intervention reduced urinary protein levels, mitigated podocyte damage in MN model rats, and improved kidney tissue pathology. Furthermore, in vitro and in vivo data revealed that SQDHD therapy significantly increased podocyte autophagy, decreased USP14 expression, and raised Beclin1's K63 ubiquitination.

CONCLUSION

These results provided a scientific rationale supporting the ability of SQDHD to substantially alleviate MN progression by inducing podocyte autophagy through the inhibition of USP14 expression.

Exploration of the pathogenesis of nephrotic syndrome and traditional Chinese medicine intervention based on gut microbiota

Nephrotic syndrome (NS) represents a prevalent syndrome among various chronic kidney disease pathologies and is known for its higher severity and worse prognosis compared with chronic glomerulonephritis. Understanding its pathogenesis and identifying more effective treatment modalities have long been a concern of kidney specialists. With the introduction of the gut-kidney axis concept and the progress in omics technologies, alterations in the gut microbiota have been observed in primary and secondary NS. This link has been extensively researched in conditions such as diabetic nephropathy and immunoglobulin A (IgA) nephropathy. Thus, dysbiosis of the gut microbiota is seen as a crucial contributing factor in NS; however, there is a lack of comprehensive reviews that elucidate the changes in the gut microbiota across different NS conditions and that describe its mechanistic role in the disease. Moreover, serving as an innate regulator of the gut microbiota, traditional Chinese medicine (TCM) has the potential to exert a profound impact on the expression of inflammation-promoting agents, decreasing the levels of endotoxins and uremic toxins. In addition, it strengthens the stability of the intestinal barrier while controlling the metabolic function of the body through its efficient modulation of the gut microbiota. This intricate process yields far-reaching consequences for NS.

Exploring PLA2R and HLA in membranous nephropathy: A narrative review of pathogenic mechanisms and emerging therapeutic potentials

Membranous Nephropathy (MN), a non-inflammatory autoimmune glomerulopathy, is a prominent cause of nephrotic syndrome, predominantly affecting Caucasian adults. It is characterized by significant thickening of the glomerular basement membrane, a direct result of immune complex deposition. Fundamental to its pathogenesis are the Phospholipase A2 receptor (PLA2R) and Human Leukocyte Antigens (HLA), which play crucial and interconnected roles. Specifically, PLA2R serves as the primary antigen, while HLA molecules facilitate MN-specific immune responses, thereby providing key insights into the disease's etiology. This study critically examines the roles of PLA2R and HLA in MN, with a particular focus on the antigenic epitopes of PLA2R. Given MN's complex nature, personalized therapeutic interventions are essential. Accordingly, targeting immunogenic epitopes has emerged as a transformative approach, aimed at modulating specific immune responses without disrupting overall immune function. Numerous studies and clinical trials have been advancing the application of these epitopes in therapeutic strategies. Nevertheless, challenges such as identifying effective epitopes, enhancing epitope-specific responses, and optimizing therapeutic dosing remain. This narrative review addresses these challenges in depth, offering a comprehensive insight into the pathology and emerging treatment strategies for MN.

Clinical characteristics of membranous nephropathy after allogeneic hematopoietic stem cell transplantation: A real-world multicenter study

Membranous nephropathy (MN) is a rare complication that can occur after allogeneic hematopoietic stem cell transplantation (allo-HSCT). MN patients may develop nephrotic syndrome or even kidney failure, which greatly affects their quality of life and prognosis. However, current knowledge regarding MN after allo-HSCT is limited. Thus, a multicenter nested case‒control study was conducted. Patients who had been diagnosed with MN after allo-HSCT were retrospectively identified at 8 HSCT centers. A total of 51 patients with MN after allo-HSCT were included. The median age of MN patients after allo-HSCT was 38 years, and the median duration from HSCT to MN was 18 months. The use of HLA-matched donors (P = 0.0102) and peripheral blood as the graft source (P = 0.0060) were identified as independent predisposing risk factors for the onset of MN after allo-HSCT. Compared to those in the control group, the incidence of extensive chronic graft-versus-host disease was greater in the MN patients (P = 0.0002). A total of 31 patients developed nephrotic syndrome. Patients receiving combination treatments of corticosteroids and immunosuppressants appeared to have better outcomes. In conclusion, MN is a rare but occasionally severe complication following HSCT and may require active treatment.

Macrocarpal B blocks the binding between the phospholipase A2 receptor and its antibodies

The pathogenic role of anti-phospholipase A2 receptor (PLA2R) antibodies in primary membranous nephropathy (MN) has been well-established. This study aimed to identify potential small-molecule inhibitors against the PLA2R-antibody interaction, offering potential therapeutic benefits. A comprehensive screening of over 4000 small-molecule compounds was conducted by ELISA to assess their inhibitory effects on the binding between the immobilized full-length extracellular PLA2R and its antibodies. The affinity of anti-PLA2R IgG from MN patients and the inhibitory efficacy of each compound were evaluated via surface plasmon resonance (SPR). Human podocyte injuries were analyzed using CCK-8 assay, wound healing assay, western blot analysis, and immunofluorescence, after exposure to MN plasma +/- blocking compound. Fifteen compounds were identified as potential inhibitors, demonstrating inhibition rates >20 % for the PLA2R-antibody interaction. Anti-PLA2R IgG exhibited a consistent affinity among patients (KD = 10-8 M). Macrocarpal B emerged as the most potent inhibitor, reducing the antigen-antibody interaction by nearly 30 % in a dose-dependent manner, comparable to the performance of the 31-mer peptide from the CysR domain. Macrocarpal B bound to the immobilized PLA2R with an affinity of 1.47 × 10-6 M, while showing no binding to anti-PLA2R IgG. Human podocytes exposed to MN plasma showed decreased podocin expression, impaired migration function, and reduced cell viability. Macrocarpal B inhibited the binding of anti-PLA2R IgG to podocytes and reduced the cellular injuries.

Glomerulus-Targeted ROS-Responsive Polymeric Nanoparticles for Effective Membranous Nephropathy Therapy

Membranous nephropathy (MN) is a common immune-mediated glomerular disease that requires the development of safe and highly effective therapies. Celastrol (CLT) has shown promise as a therapeutic molecule candidate, but its clinical use is currently limited due to off-target toxicity. Given that excess levels of reactive oxygen species (ROS) contributing to podocyte damage is a key driver of MN progression to end-stage renal disease, we rationally designed ROS-responsive cationic polymeric nanoparticles (PPS-CPNs) with a well-defined particle size and surface charge by employing poly(propylene sulfide)-polyethylene glycol (PPS-PEG) and poly(propylene sulfide)-polyethylenimine (PPS-PEI) to selectively deliver CLT to the damaged glomerulus for MN therapy. Experimental results show that PPS-CPNs successfully crossed the fenestrated endothelium, accumulated in the glomerular basement membrane (GBM), and were internalized by podocytes where rapid drug release was triggered by the overproduction of ROS, thereby outperforming nonresponsive CLT nanotherapy to alleviate subepithelial immune deposits, podocyte foot process effacement, and GBM expansion in a rat MN model. Moreover, the ROS-responsive CLT nanotherapy was associated with significantly lower toxicity to major organs than free CLT. These results suggest that encapsulating CLT into PPS-CPNs can improve efficacy and reduce toxicity as a promising treatment option for MN.

Comparison of tacrolimus with or without prednisone therapy in primary membranous nephropathy: a retrospective clinical study

Previous studies showed tacrolimus monotherapy and dual therapy with tacrolimus and prednisone as effective treatment modalities in managing membranous nephropathy. However, few studies have compared these therapeutic regimens. The patients were divided into two groups based on the treatment regimen: (1) tacrolimus and prednisone dual therapy (T + P group, n = 67) treatment group; and (2) tacrolimus monotherapy (T group, n = 65) or the control group. Propensity matching method and subgroup analysis to eliminate the bias in the relationship between the treatment regimen and the outcomes. The mean remission times were 20.33 ± 2.75 weeks at T group and 9.50 ± 1.81 weeks at T + P group. The T group had a remission rates of 73.33, 76.66 and 66.66% at 12weeks, 24weeks and 48weeks, while the T + P group had a remission rate of 81.66, 86.66, 91.66%; At the follow-up of 48 weeks, the relapse rate for the T group was 21.66%, and that for the T + P group was 5%. The anti-PLA2R ab is positive and therapy may be the independent risk factors for predicting remission. Tacrolimus and low-dose prednisone dual therapy is efficacious in managing MN and lowers the recurrence rate in clinical practice.

miR-664a-5p promotes experimental membranous nephropathy progression through HIPK2/Calpain1/GSα-mediated autophagy inhibition

We previously found that miR-664a-5p is specifically expressed in urinary exosomes of idiopathic membranous nephropathy (IMN) patients. Homeodomain-interacting protein kinase 2 (HIPK2), a nuclear serine/threonine kinase, plays an important role in nephropathy. But the function of these factors and their connection in MN are unclear. To investigate the function and mechanism of miR-664a-5p in MN, the miR-664a-5p expression in HK-2 cells, exosomes, podocytes and renal tissues were studied, as well as cell growth and apoptosis of these cells, the binding of miR-664a-5p to HIPK2 mRNA, the levels of relative proteins and autophagy. The MN progression in MN mice model was also studied. Albumin increased the miR-664a-5p content and apoptosis of HK-2 cells, which was blocked by miR-664a-5p antagomir. miR-664a-5p bound to the 3' UTR of HIPK2 mRNA, resulting in the up-regulation of Calpain1, GSα shear and the inhibition of autophagy level. Autophagy inhibitor CQ blocked the protective effect of miR-664a-5p antagomir, HIPK2 overexpression, Calpain inhibitor SJA6017 on albumin-mediated injury. MiR-664a-5p from albumin-treated HK-2 cells could be horizontally transported to podocytes through exosomes. Exosomes from albumin-treated HK-2 cells promoted progression of MN mice, AAV-Anti-miR-664-5p (mouse homology miRNA) could improve them. Albumin increases the miR-664a-5p level and causes changes of HIPK2/Calpain1/GSα pathway, which leads to autophagy inhibition and apoptosis up-regulation of renal tubular epithelial cells. miR-664a-5p can horizontally enter podocytes through exosomes resulting in podocytes injury. Targeted inhibition of miR-664a-5p can reduce the apoptosis of renal tubule cells and podocytes, and may improve the MN progression.

Nephrotic Syndrome: A Review

Nephrotic syndrome (NS) is characterized by hypoalbuminemia, severe proteinuria, and peripheral edema, frequently in conjunction with hyperlipidemia. Individuals usually show symptoms of weariness and swelling, but no signs of serious liver damage or cardiac failure. With characteristic medical symptoms and evidence of hypoalbuminemia and severe proteinuria, NS can be diagnosed. The majority of NS episodes are classified as unexplained or primary; the most prevalent histopathological subgroups of primary NS in people are focal segmental glomerulosclerosis and membraneous nephropathy. Thrombosis of the veins with high cholesterol levels is a significant NS risk. Acute renal damage and infection are further possible side effects. The pathobiochemistry of NS involves alterations in genes that affect the selectivity of the kidneys and abnormalities in proteins related to podocytes. Understanding the molecular mechanisms that influence these processes is crucial to developing specific and targeted therapeutic approaches. The need for invasive renal biopsies throughout the diagnosis process may be lessened by the development of non-invasive nephrotic syndrome biomarkers, such as microRNAs. Corticosteroids are frequently used as the initial line of defense in NS treatment. However, some individuals need other treatments since a resistant type of NS also exists. The use of calcineurin inhibitors, mycophenolate mofetil, and rituximab is mentioned in the text, along with current research to identify safer and more efficient therapeutic choices. The complicated kidney condition NS has several underlying causes and symptoms. For the diagnosis of this ailment as well as the creation of focused therapies, an understanding of the pathophysiology and the identification of possible biomarkers are essential.

Virtual diagnosis of diabetic nephropathy using metabolomics in place of kidney biopsy: The DIAMOND study

AIMS

To explore the clinical factors and urinary metabolites that predict biopsy-confirmed diabetic nephropathy (DN) in patients with type 2 diabetes mellitus (T2DM).

METHODS

Data from the medical records of 126 patients with T2DM who underwent kidney biopsy between January 2010 and October 2020 at a single-center were retrospectively reviewed to investigate the clinical factors that predict DN. Urine samples were collected to perform urine metabolomics in patients with T2DM divided by biopsy-confirmed DN, immunoglobulin A, and membranous nephropathy, and a control group of healthy participants. Each group comprised 11 age- and sex-matched participants. A prediction model was developed using a combination of clinical factors and urinary metabolites, and a multivariate receiver operating characteristic (ROC) analysis was conducted.

RESULTS

Age, presence of proliferative diabetic retinopathy, T2DM duration, and hemoglobin A1c levels were clinical factors predictive of DN. Four urinary metabolites (alanine, choline, N-phenylacetylglycine, and trigonelline) had variable importance in projection scores > 1 and were predictive of DN. When conducting multivariate ROC analysis with a combination of clinical factors and urinary metabolites, the area under the curve was 1.000.

CONCLUSIONS

The combination of clinical factors and urinary metabolites is highly valuable for predicting biopsy-confirmed DN in patients with T2DM.

Crocin improves the renal autophagy in rat experimental membranous nephropathy via regulating the SIRT1/Nrf2/HO-1 signaling pathway

Membranous nephropathy (MN) is a glomerular disease. Crocin is isolated from saffron and gardenia. Its antioxidant, anti-inflammatory, anti-hyperlipidemic, anti-atherosclerotic, anti-tumor, free-radical scavenging and neuroprotective activities have been well established. We investigated the biological functions of crocin and its related mechanisms in MN. We established an experimental passive Heymann nephritis (PHN) rat model induced by anti-Fx1A antiserum. The rats were divided into sham, sham + crocin, PHN, PHN + crocin, and PHN + enalapril groups. Blood samples and kidneys of rats were collected for estimation of biochemical parameters in serum and oxidative stress indicators in kidney tissues. Histopathological changes of renal tissues were evaluated by hematoxylin and eosin, periodic acid-Schiff (PAS) and Masson staining. The podocyte number was estimated by immunohistochemistry staining of Wilms tumor type 1 (WT1). The deposition of rat anti-rabbit IgG antibodies, complement C3 and C5b-9 was detected by immunofluorescence staining. Western blotting was performed to measure the levels of Sirtuin 1 (Sirt1), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1) and apoptosis-related proteins. The total cholesterol, triglycerides, creatinine, blood urea nitrogen, urine volume and urine albumin of PMN rats were significantly reduced by crocin. Additionally, crocin attenuated the renal histopathological changes. Moreover, the oxidative stress damage and podocyte loss and immune injury were relieved by crocin in PHN rats. Mechanistically, crocin administration activated the Sirt1/Nrf2/HO-1 pathways. The results provide a scientific basis that crocin could alleviate MN by inhibiting immune injury and podocyte damage through activating the Sirt1/Nrf2/HO-1 pathways.

Contactin-1 links autoimmune neuropathy and membranous glomerulonephritis

Membranous glomerulonephritis (MGN) is a common cause of nephrotic syndrome in adults, mediated by glomerular antibody deposition to an increasing number of newly recognised antigens. Previous case reports have suggested an association between patients with anti-contactin-1 (CNTN1)-mediated neuropathies and MGN. In an observational study we investigated the pathobiology and extent of this potential cause of MGN by examining the association of antibodies against CNTN1 with the clinical features of a cohort of 468 patients with suspected immune-mediated neuropathies, 295 with idiopathic MGN, and 256 controls. Neuronal and glomerular binding of patient IgG, serum CNTN1 antibody and protein levels, as well as immune-complex deposition were determined. We identified 15 patients with immune-mediated neuropathy and concurrent nephrotic syndrome (biopsy proven MGN in 12/12), and 4 patients with isolated MGN from an idiopathic MGN cohort, all seropositive for IgG4 CNTN1 antibodies. CNTN1-containing immune complexes were found in the renal glomeruli of patients with CNTN1 antibodies, but not in control kidneys. CNTN1 peptides were identified in glomeruli by mass spectroscopy. CNTN1 seropositive patients were largely resistant to first-line neuropathy treatments but achieved a good outcome with escalation therapies. Neurological and renal function improved in parallel with suppressed antibody titres. The reason for isolated MGN without clinical neuropathy is unclear. We show that CNTN1, found in peripheral nerves and kidney glomeruli, is a common target for autoantibody-mediated pathology and may account for between 1 and 2% of idiopathic MGN cases. Greater awareness of this cross-system syndrome should facilitate earlier diagnosis and more timely use of effective treatment.

Chronic Graft-versus-host Disease-associated Membranous Nephropathy Following Bone Marrow Transplantation, Successfully Treated with Rituximab

A 67-year-old woman who had undergone bone marrow transplantation 2 years previously for acute myeloid leukemia (AML) developed complications of chronic graft-versus-host disease (cGVHD). She thereafter also developed nephrotic syndrome, and membranous nephropathy (MN) was diagnosed by a renal biopsy. Although the causative antigens of the MN were not detected, immunofluorescence staining showed codominant deposition of immunoglobulins G2 and G3, a finding indicating secondary MN, thereby suggesting an association between MN and cGVHD. Rituximab treatment was initiated, and her nephrotic syndrome gradually improved without relapse of AML. Our present case suggests that rituximab is a safe and effective therapeutic option for cGVHD-associated MN.

Membranous Nephropathy With Extensive Tubular Basement Membrane Deposits Following Allogeneic Hematopoietic Cell Transplant: A Report of 5 Cases

Tubular basement membrane (TBM) deposits are very uncommon in non-lupus membranous nephropathy. We report 5 patients with membranous nephropathy and extensive TBM deposits following allogeneic hematopoietic cell transplant. Patients presented with nephrotic syndrome (3 also had acute kidney injury) late post-transplant in association with chronic graft-versus-host disease (cGVHD). Kidney biopsies revealed global subepithelial and extensive TBM immune complex deposits, accompanied by acute tubular injury (n = 4) and tubulointerstitial inflammation (n = 4). Proteomic analysis of glomeruli in 4 cases identified PLA2R in 1, with no significant protein spectra for PLA2R, THSD7A, EX1/2, NELL-1, PCDH7, NCAM1, or SEMA3B detected in the remaining 3. On follow-up (for a mean 42 months), 4 patients had complete and 1 partial remission following prednisone and/or rituximab therapy. We propose that membranous nephropathy with extensive TBM deposits is a distinctive clinicopathologic lesion associated with allogeneic hematopoietic cell transplant. Pathogenesis likely involves cGVHD-driven antibodies against glomerular and TBM components, the identity of which remains to be elucidated.

Hematopoietic Stem Cell Transplant-Membranous Nephropathy Is Associated with Protocadherin FAT1

BACKGROUND

Membranous nephropathy (MN) is a common cause of proteinuria in patients receiving a hematopoietic stem cell transplant (HSCT). The target antigen in HSCT-associated MN is unknown.

METHODS

We performed laser microdissection and tandem mass spectrometry (MS/MS) of glomeruli from 250 patients with PLA2R-negative MN to detect novel antigens in MN. This was followed by immunohistochemical (IHC)/immunofluorescence (IF) microscopy studies to localize the novel antigen. Western blot analyses using serum and IgG eluted from frozen biopsy specimen to detect binding of IgG to new 'antigen'.

RESULTS

MS/MS detected a novel protein, protocadherin FAT1 (FAT1), in nine patients with PLA2R-negative MN. In all nine patients, MN developed after allogeneic HSCT (Mayo Clinic discovery cohort). Next, we performed MS/MS in five patients known to have allogeneic HSCT-associated MN (Cedar Sinai validation cohort). FAT1 was detected in all five patients by MS/MS. The total spectral counts for FAT1 ranged from 8 to 39 (mean±SD, 20.9±10.1). All 14 patients were negative for known antigens of MN, including PLA2R, THSD7A, NELL1, PCDH7, NCAM1, SEMA3B, and HTRA1. Kidney biopsy specimens showed IgG (2 to 3+) with mild C3 (0 to 1+) along the GBM; IgG4 was the dominant IgG subclass. IHC after protease digestion and confocal IF confirmed granular FAT1 deposits along the GBM. Lastly, Western blot analyses detected anti-FAT1 IgG and IgG4 in the eluate obtained from pooled frozen kidney biopsy tissue and in the serum of those with FAT1-asssociated MN, but not from those with PLA2R-associated MN.

CONCLUSIONS

FAT1-associated MN appears to be a unique type of MN associated with HSCT. FAT1-associated MN represents a majority of MN associated with HSCT.

Critical evaluation of cancer risks in glomerular disease

The increased cancer incidence in patients with glomerular disease can be secondary to an intrinsic immune dysfunction associated with the disease or/and extrinsic factors, especially immunosuppressants. The treatment for paraneoplastic glomerulopathy is different from primary glomerular disease. Immunosuppressive therapy often used for primary glomerulopathy may aggravate concomitant cancers in patients with paraneoplastic glomerulopathy. In membranous nephropathy (MN), measurement of serum circulating autoantibodies against podocyte transmembrane glycoprotein M-type phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain-containing 7A (THSD7A), immunohistochemical staining of kidney tissue for glomerular PLA2R, THSD7A, neural epidermal growth factor-like 1 protein (NELL-1) and specific types of immunoglobulin G (IgG) may be useful adjuncts when screening for underlying malignancies. This review addresses overall cancer risks in individuals with glomerular diseases and employment of biomarkers available for MN. We propose a scheme of screening of cancers frequently reported in the setting of glomerular disease.

Analysis of glomerular PLA2R efficacy in evaluating the prognosis of idiopathic membranous nephropathy in the background of different serum anti-PLA2R levels

OBJECTIVE

To verify glomerular PLA2R antigen and serum PLA2R antibody expression in membranous nephropathy as well as to explore glomerular PLA2R efficacy in evaluating the prognosis of idiopathic membranous nephropathy (IMN) in the background of different serum anti-PLA2R levels.

METHODS

We retrospectively analyzed 155 patients who were diagnosed with IMN by kidney biopsy. Patients were divided into six groups according to their serum PLA2R antibody or glomerular PLA2R antigen positiveness and the level of serum anti-PLA2R titer. Both clinical features and pathological characteristics were recorded, and the remission time was compared among groups. Correlation between clinical figures and the anti-PLA2R titer or semi-quantity of glomerular PLA2R antigen was detected.

RESULTS

A positive correlation between time to partial remission and serum anti-PLA2R titer was found. Among patients with serum anti-PLA2R titer <150 RU/ml, there were shorter remission time in negative glomerular PLA2R antigen group compared with positive glomerular PLA2R antigen, and a positive correlation between time to complete remission and semi-quantity of glomerular PLA2R antigen was found.

CONCLUSION

Both glomerular PLA2R antigen and serum anti-PLA2R play a role in disease presentation and prognosis in primary membranous nephropathy. Glomerular PLA2R antigen has a major role on disease prognosis when serum anti-PLA2R titer is less than 150RU/ml, while serum anti-PLA2R has predominant role in IMN prognosis when serum anti-PLA2R titer is above 150RU/ml.

Definition of IgG Subclass-Specific Glycopatterns in Idiopathic Membranous Nephropathy: Aberrant IgG Glycoforms in Blood

The podocyte injury, and consequent proteinuria, that characterize the pathology of idiopathic membranous nephropathy (IMN) is mediated by an autoimmune reaction against podocyte antigens. In particular, the activation of pathways leading to abundant renal deposits of complement is likely to involve the binding of mannose-binding lectin (MBL) to aberrant glycans on immunoglobulins. To obtain a landscape of circulatory IgG Fc glycosylation characterizing this disease, we conducted a systematic N-glycan profiling study of IgG1, 2, and 4 by mass spectrometry. The cohort included 57 IMN patients, a pathological control group with nephrotic syndrome (PN) (n = 20), and 88 healthy control subjects. The effect of sex and age was assessed in all groups and controlled by rigorous matching. Several IgG Fc glycan traits were found to be associated with IMN. Interestingly, among them, only IgG4-related results were specific for IMN and not for PN. Hypo-galactosylation of IgG4, already shown for IMN, was observed to occur in the absence of core fucose, in line with a probable increase of pro-inflammatory IgG. In addition, elevated levels of fucosylated IgG4, along with low levels of hybrid-type glycans, were detected. Some of these IgG4 alterations are likely to be more pronounced in high PLA2R (phospholipase A2 receptor) patients. IgG Fc glycosylation patterns associated with IMN warrant further studies of their role in disease mechanisms and may eventually enrich the diagnostic spectrum regarding patient stratification.

Prevalence of neural epidermal growth factor-like 1- and exostosin 1/exostosin 2-associated membranous nephropathy: a single-center retrospective study in Japan

Membranous nephropathy (MN) is the leading cause of nephrotic syndrome in adults. We previously reported that the prevalence of phospholipase A2 receptor (PLA2R)- and thrombospondin type 1 domain containing 7A (THSD7A)-associated MN patients in Japan is 52.7% and 9.1%, respectively. In addition to PLA2R and THSD7A, we assessed the presence of newly discovered target antigens, neural epidermal growth factor-like 1 (NELL-1), semaphorin 3B (SEMA3B), and exostosin 1/exostosin 2 (Ext1/Ext2), in renal specimens from patients with primary and secondary MN by immunohistochemistry. We found enhanced glomerular staining of PLA2R, THSD7A, NELL-1, and Ext1/Ext2 in 53.6%, 8.7%, 1.5%, and 13.0% of the renal samples, respectively, in patients with primary MN. None of the patient specimens showed enhanced staining of SEMA3B. Enhanced glomerular staining of PLA2R, NELL-1, and Ext1/Ext2 was detected in 5.7%, 8.6%, and 22.9% of the patients with secondary MN, respectively. Based on our findings, we recommend the assessment of PLA2R, THSD7A and NELL-1 in addition to clinical information and IgG4 staining to differentiate between primary and secondary MN. This would aid in distinguishing secondary MN patients from primary MN patients who coincidentally have some secondary characteristics.

MicroRNAs: Potential mediators between particulate matter 2.5 and Th17/Treg immune disorder in primary membranous nephropathy

Primary membranous nephropathy (PMN), is an autoimmune glomerular disease and the main reason of nephrotic syndrome in adults. Studies have confirmed that the incidence of PMN increases yearly and is related to fine air pollutants particulate matter 2.5 (PM2.5) exposure. These imply that PM2.5 may be associated with exposure to PMN-specific autoantigens, such as the M-type receptor for secretory phospholipase A2 (PLA2R1). Emerging evidence indicates that Th17/Treg turns to imbalance under PM2.5 exposure, but the molecular mechanism of this process in PMN has not been elucidated. As an important indicator of immune activity in multiple diseases, Th17/Treg immune balance is sensitive to antigens and cellular microenvironment changes. These immune pathways play an essential role in the disease progression of PMN. Also, microRNAs (miRNAs) are susceptible to external environmental stimulation and play link role between the environment and immunity. The contribution of PM2.5 to PMN may induce Th17/Treg imbalance through miRNAs and then produce epigenetic affection. We summarize the pathways by which PM2.5 interferes with Th17/Treg immune balance and attempt to explore the intermediary roles of miRNAs, with a particular focus on the changes in PMN. Meanwhile, the mechanism of PM2.5 promoting PLA2R1 exposure is discussed. This review aims to clarify the potential mechanism of PM2.5 on the pathogenesis and progression of PMN and provide new insights for the prevention and treatment of the disease.

Acidic Stigma maydis polysaccharides protect against podocyte injury in membranous nephropathy by maintenance of glomerular filtration barrier integrity and gut-kidney axis

MN mice models were induced by C-BSA, and we found that acidic stigma maydis polysaccharides  maintained the integrity of the glomerular filtration barrier by promoting slit diaphragm proteins expression and PI3K/AKT signaling.

Sanqi Oral Solution Mitigates Proteinuria in Rat Passive Heymann Nephritis and Blocks Podocyte Apoptosis via Nrf2/HO-1 Pathway

Idiopathic membranous nephropathy (IMN) is the most common pathological type in adult nephrotic syndrome where podocyte apoptosis was found to mediate the development of proteinuria. Sanqi oral solution (SQ), an effective Chinese herbal preparation clinically used in treatment of IMN for decades, plays an important role in reducing proteinuria, but the underlying mechanisms have not been fully elucidated yet. The current study tested the hypothesis that SQ directly lessens proteinuria in IMN by reducing podocyte apoptosis. To investigate the effects of SQ, we established the experimental passive Heymann nephritis (PHN) rat model induced by anti-Fx1A antiserum in vivo and doxorubicin hydrochloride (ADR)-injured apoptotic podocyte model in vitro. SQ intervention dramatically reduced the level of proteinuria, together with the rat anti-rabbit IgG antibodies, complement C3, and C5b-9 deposition in glomerulus of PHN rats, accompanied by an elevation of serum albumin. Protein expression of synaptopodin, marker of podocyte injury, restored after SQ administration, whereas the electron microscopic analysis indicated that fusion of foot processes, and the pachynsis of glomerular basement membrane was markedly diminished. Further studies showed that SQ treatment could significantly inhibit podocyte apoptosis in PHN rats and ADR-injured podocytes, and protein levels of Cleaved Caspase-3 or the ratio of Bax/Bcl-2 were significantly decreased with SQ treatment in vivo or in vitro. Moreover, we found that the nuclear factor erythroid 2–related factor-2/heme oxygenase 1 (Nrf2/HO-1) pathway mediated the anti-apoptosis effective of SQ in podocyte. Thus, SQ mitigates podocyte apoptosis and proteinuria in PHN rats via the Nrf2/HO-1 pathway.

Ameliorated membranous nephropathy activities of two ethanol extracts from corn silk and identification of flavonoid active compounds by LC-MS2

The current study looks to evaluate the effect of corn silk flavonoids on membranous nephropathy (MN). Polyamide resin (PR) can be used to enrich corn silk ethanol extract (CSEE) to obtain flavonoid-rich extract (PR-CSEE), the total flavonoid content (TFC) of which we found to be 57.4%. The results of scanning electron microscope, Fourier-transform infrared, and high-performance liquid chromatography analyses determined that PR-CSEE and CSEE have different structural characteristics, but that PR-CSEE has higher TFC. MN mice models were induced by cationic bovine serum albumin, and we found that PR-CSEE administration reduced urine protein levels markedly, while renal function, glomerular atrophy, inflammatory infiltration, and in-serum immunoglobulin G and complement 3 content were improved. Through LC-MS² spectrometry analysis, we pinpointed the 12 major flavonoid active compounds in PR-CSEE. These findings suggest that PR-CSEE can act as a potential functional food material by which to improve MN.

Clinicopathological characteristics and prognosis of hepatitis B associated membranous nephropathy and idiopathic membranous nephropathy complicated with hepatitis B virus infection

The main objective of this study is to analyze the clinical and pathological features and prognosis of patients with Hepatitis B associated membranous nephropathy (HBV-MN) and idiopathic membranous nephropathy (IMN) complicated with hepatitis B virus (HBV) infection. This study will provide more basis for diagnosis and prognosis evaluation. A total of 50 patients with HBV-MN were included in this study. 56 IMN patients complicated with HBV infection diagnosed during the same period formed the control group. Parameters including blood routine, urine routine and plasma levels of albumin (ALB), serum creatinine (SCR), blood urea nitrogen (BUN), urea acid (UA), total cholesterol (T-CHO), triglycerides (TG), complement C3 and C4, glutamic pyruvic transaminase (ALT), glutamic pyruvic transaminase (AST), 24-h urinary protein quantification (24 h-TP), renal phospholipase A2 receptor (PLA₂R) and HBV related markers during the hospitalization and outpatient follow-up study period were collected for all the patients. The proportion of male patients was high in both groups. The average age of the HBV-MN group was 37.2 ± 14.187 years old, it was younger compared with the IMN group (P = 0.003). Nephrotic syndrome was the major clinical manifestation among patients. There was no significant difference between the two groups in the levels of anemia, microscopic hematuria, renal dysfunction, liver dysfunction, liver cirrhosis. The level of serum C3 and C4 in the HBV-MN group was lower compared with the IMN group (P = 0.002, P = 0.014). In the HBV-MN group, serum HBV markers were negative in 6 (12%) patients, 4 patients (8%) were positive for PLA₂R in serum, and 5 patients (10%) were positive for PLA₂R in renal tissue. Stronger IgG1 and C1q and weaker IgG4 staining were found in HBV-MN group renal tissues (P = 0.003, P = 0.025, and P = 0.001, respectively). There were no statistical differences compared with serum and renal PLA₂R between HBV-MN and IMN groups (P = 0.098, P = 0.109). During the 1-year follow-up, there was no significant difference in complete remission rate between the two groups (P = 0.7739). Renal biopsy is crucial to diagnose HBV-MN. IgG subtypes in the HBV-MN group were mainly IgG1 deposition, while those in IMN complicated with HBV infection group were mainly IgG4 deposition. When HBV-associated antigen and PLA₂R are present in renal tissue, lower level of serum C3 and C4, high intensity of renal C1q and IgG1 is more supportive of HBV-MN. The positive of PLA₂R in serum and renal tissue in differentiating HBV from IMN complicated with HBV infection remains to be discussed.

Long non-coding RNA Neat1 triggers renal tubular epithelial cell apoptosis via activating BH3-only protein in membranous nephropathy

BACKGROUND AND OBJECTIVE

Membranous nephropathy (MN) is an autoimmune disease. The up-regulation of the long non-coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (Neat1) has been found in MN but the mechanism is still unclear. Here, we explored the effect and the underlying mechanism of lncRNA Neat1 on the apoptosis of renal tubular epithelial cells in MN.

METHODS

Albumin-stimulated E11 podocytes and proximal tubular epithelial cells in vitro and the cationic-bovine serum albumin-induced MN mouse model in vivo were established. The expression of Neat1 in E11 podocytes, renal tubular epithelial cells, and renal tubules and the mRNA expression of BH3-only (the Bcl-2 homology 3-only) proteins were determined by quantitative reverse transcription-polymerase chain reaction. Levels of Cleaved Caspase 3, 6, 7, and Noxa were examined by western blotting. The number of apoptotic cells was detected by flow cytometry. Cellular proliferation was determined by 5-Ethynyl-2'-deoxyuridine and Cell Counting Kit-8 assay. Interactions between BH3-only protein Noxa and Bcl-2 as well as Bcl-xL were evaluated with co-immunoprecipitation.

RESULTS

The expression of lncRNA Neat1 was unchanged in albumin-stimulated E11 podocytes, but it was up-regulated in albumin-stimulated renal tubular epithelial cells and MN renal tubule tissues and there was a time-dependent increase in vivo. In the albumin-stimulated proximal tubular epithelial cells, overexpression of Neat1 could increase apoptosis and decrease proliferation. In turn, interference with Neat1 reduced apoptosis and increased proliferation accordingly. The mRNA expression levels of BH3-only proteins (Bad, Bim, Bid, Puma, Noxa) were detected with qRT-PCR, the results indicated that after overexpression of Neat1, mRNA and protein levels of Noxa were significantly increased, and the interference with BH3-only protein Noxa alleviated apoptosis of renal tubular epithelial cells in vitro.

CONCLUSION

In our study, we proved that lncRNA Neat1 promoted the development of MN by inducing apoptosis and this effect may be exerted by inhibiting the anti-apoptotic protein activity mediated by Noxa.

Advances in antigens associated with Idiopathic Membranous Nephropathy

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults. Idiopathic MN (IMN), one of the forms of MN, usually has an unknown etiology. IMN is described as an autoimmune disease, and its pathogenesis is quite complex. The discovery of the M-type phospholipase A₂ receptor (PLA₂R) plays an important role in promoting our understanding of IMN, although the exact mechanisms of its occurrence and development are still not completely clear. Other target antigens have been discovered one after another, as considerable progress has been made in the molecular pathomechanisms of IMN. Here, we review the findings about the target antigens associated with IMN in recent years. It is hoped that this article can provide researchers with some scientific issues or innovative ideas for future studies of IMN, which will provide clinicians with more knowledge about further improving their abilities to provide better medical care for IMN patients.

Inhibition of the Wnt/β-catenin signaling pathway reduces autophagy levels in complement treated podocytes

In idiopathic membranous nephropathy, the complement membrane attack complex, more commonly referred to as complement 5b-9 (C5b-9), induces glomerular epithelial cell injury and proteinuria. C5b-9 can also activate numerous mechanisms that restrict or facilitate injury. Recent studies suggest that autophagy and the canonical Wnt signaling pathway serve an important role in repairing podocyte injury. However, the effect of C5b-9 on these pathways and the relationship between them remains unclear. The aim of the present study was to show the effect of C5b-9 on the Wnt/β-catenin signaling pathway and autophagy in podocytes in vitro. Levels of relevant indicators were detected by immunofluorescence staining and capillary western immunoassay. C5b-9 serum significantly activated the Wnt/β-catenin signaling pathway and promoted autophagy. Treatment with Dickkopf-related protein 1 (DKK1), a Wnt/β-catenin pathway blocker, protected podocytes from injury and significantly inhibited autophagy. The results indicated that inhibition of the Wnt/β-catenin pathway physiologically activated autophagy. The results indicated that C5b-9 resulted in a decrease in Akt in podocytes. However, the podocytes preincubated with DKK1 and then attacked by C5b-9 showed an increase in Akt levels. This may explain the observation that blocking the Wnt/β-catenin signaling pathway attenuated C5b-9 podocyte damage, while inhibiting autophagy. The results of the present study also suggest that regulation of these two pathways may serve as a novel method for the treatment of idiopathic membranous nephropathy.

Comparison of 3 anti-PLA2R inmmunoassaysfor the diagnosis of idiopathic membranous nephropathy in an european population. A pilot study

Membranous nephropathy (MN) is one of the most frequent causes of nephrotic syndrome. Renal biopsy is nowadays the gold standard for the diagnosis of MN. The presence of circulating PLA2R antibody is a very specific tool for the diagnosis of this disease, especially associated with primary or idiopathic MN (IMN), even though it can be also found in a small proportion of patients with secondary MN (SMN). This pilot study compares three different techniques for the detection of anti-PLA2R autoantibodies (immunofluorescence, ELISA immunoassay, and multiplex laser bead technology). Serum of 12 IMN and 9 SMN patients was obtained at diagnosis. Additionally, we employed serum samples of 15 healthy volunteers. From our patient cohort, we obtained a 7.75 RU/ml cut-off for the ELISA and 3104 MFI for the Luminex assays. The agreement between the three techniques improved considerably when applying the new cut-off points. As several authors have suggested, cut-offs may be calculated for each specific population instead of establishing global cut-off points. Patients with IMN showed significantly lower serum albumin levels and higher 24 h proteinuria compared to those with SMN. Analysis of ROC curves suggests that ELISA and LUMINEX assays are more useful than biochemical variables to differentiate patients with IMN and SMN. This pilot study contributes to confirming that the combination of ELISA and Luminex assays provide excellent sensitivity and specificity for the identification of IMN.

A cohort study of membranous nephropathy, primary or secondary

Background

Although IgG4 deposit against phospholipase A2 receptor (anti-PLA2R) is predominantly presented in the renal biopsy of patients with primary membranous nephropathy (MN), its diagnostic value of this immune complex has not been fully established.

Methods

In this cohort study, 108 biopsy-proven MN patients with proteinuria were evaluated during two years follow up and were divided into primary and secondary groups. Renal biopsy specimens were pathologically assessed for IgG4 and PLA2R depositions by immunohistochemistry (IHC). Therefore, the relationships between staining severity, MN type and total proteinuria in all patients were determined.

Results

Of 108 patients, 73.1% had primary MN and 26.9% were diagnosed as secondary form. IHC staining in patients with primary MN was positive for PLA2R in 76 (96.2%) and IgG4 in 68 (86.1%). Cases with positive PLA2R expression had a significantly higher rate among patients with mild to moderate stages (P = 0.03). No significant relationship was found between intensity of PLA2R and IgG4 deposits with proteinuria and serum creatinine. Based on our data, double positivity/negativity of PLA2R and IgG4 expression adds prominent information to the clinical data and were found to be useful and robust biomarkers for detection of primary MN patients with high sensitivity and specificity (97.1 and 96.3% respectively, PPV = 98.5% and NPV = 92.9%).

Conclusions

Simultaneously expression of PLA2R and IgG4 in renal biopsy specimens of patients with MN could possibly be used as a potential diagnostic method to distinguish primary from secondary MN and also pathological severity of the disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02338-6.

Treatment of exostosin 1-associated membranous lupus nephritis with multiple low doses of rituximab: A case report

RATIONALE

Membranous glomerulonephritis (MN) is the leading cause of nephrotic syndrome in adults and is classified as primary or secondary. Secondary MN accounts for 20% to 30% of all MN cases and can arise from a number of conditions, including autoimmune diseases. Recently exostosin 1/exostosin 2 (EXT1/EXT2) have been identified as the common antigens in secondary autoimmune MN and are present in cases of pure membranous lupus nephritis (LN). The treatment of EXT1/EXT2-associated MN remains elusive.

PATIENT CONCERNS

We present the case of a 15-year-old female who presented with nephrotic syndrome, positive ANA and dsDNA, and low serum complements. A renal biopsy revealed pure membranous nephritis with IgG and C3 deposition. EXT1 was found along the glomerular capillary walls and stained positive, while phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) were negative.

DIAGNOSIS

The patient was diagnosed with ETX1-associated membranous LN.

INTERVENTIONS

She was treated with prednisone and multiple low-dose rituximab (4 200 mg doses, approximately every 2 months, based on CD19+ cells counts).

OUTCOMES

The patient had complete remission within 8 months later, and she remained in remission for the 16-month period of follow-up.

LESSONS

To our knowledge, this is the first case of EXT1-associated MN that has been successfully treated by multiple low-dose rituximab. Further studies can investigate the optimal dosage and treatment protocol.

PLA2R1 and HLA-DQA1 gene variations in idiopathic membranous nephropathy in South China

INTRODUCTION

Associations of variations in PLA2R1 and HLA-DQA1 genes with susceptibility to idiopathic membranous nephropathy (IMN) have been well documented. Association with spontaneous remission, however, is poorly defined in the Chinese Han population.

METHODS

A Chinese cohort of 117 IMN patients and 138 healthy controls were recruited between July 2009 and November 2019. Case-control studies for single-nucleotide polymorphisms (SNPs) within HLA-DQA1 (rs2187668) and PLA2R1 (rs35771982, rs4664308, rs3749117, rs3749119) genes were performed. The contributions of these polymorphisms to predict susceptibility, titre of autoantibodies against the M-type phospholipase A2 receptor (anti-PLA2R1), glomerular PLA2R1 expression, and spontaneous remission were analysed.

RESULTS

We found that variations in PLA2R1 (SNPs rs35771982, rs4664308, rs3749117) were strongly associated with IMN susceptibility, while SNP (rs2187668) within HLA-DQA1 did not increase the risk of IMN. All SNPs in PLA2R1 and HLA-DQA1 were not statistically associated with anti-PLA2R1 titre, glomerular PLA2R1 expression and spontaneous remission after Bonferroni correction (P>0.0167). Clinical and pathological parameters such as lower levels of serum albumin, higher levels of anti-PLA2R1 and glomerular PLA2R1 expression were independent risk factors for non-spontaneous remission.

CONCLUSION

This study confirms that variations in PLA2R1 (SNPs rs35771982, rs4664308, rs3749117) are risk factors for IMN. We found excellent association of serum albumin level, anti-PLA2R1 titre and glomerular PLA2R1 positivity with non-spontaneous remission in IMN.

[Renal involvement in Sjögren's syndrome]

Primary Sjögren syndrome is an autoimmune disorder characterized by lymphoplasmacytic infiltration of the exocrine (salivary and lachrymal) glands resulting in sicca symptoms (dryness). Systemic complications can occur in primary Sjögren syndrome, but renal involvement is rare, affecting<10% patients. The most frequent form of nephropathy in primary Sjögren syndrome is tubulointerstitial nephritis, where infiltration of the kidney by plasma cells is a key feature and shows similarity to the lymphoplasmacytic infiltration of the salivary glands. Electrolyte disturbances may occur in primary Sjögren syndrome, such as renal distal tubular acidosis, diabetes insipidus, Gitelman syndrome, or Fanconi syndrome. Glomerular involvement is less frequently detected in patients with primary Sjögren syndrome, but can take the form of membranoproliferative glomerulonephritis secondary to cryoglobulinaemia. The renal prognosis in patients with primary Sjögren syndrome and TIN or glomerular disease is usually good, but the risk of chronic kidney disease remains significant for some patients. Appropriate screening must be performed at least once a year in patients with systemic primary Sjögren syndrome in order to facilitate the early detection of renal complications. In this Review, we discuss the epidemiology, pathophysiology, differential diagnosis, and treatment of renal disease in primary Sjögren syndrome.

Curcumin Improves the Renal Autophagy in Rat Experimental Membranous Nephropathy via Regulating the PI3K/AKT/mTOR and Nrf2/HO-1 Signaling Pathways

Membranous nephropathy (MN, also known as membranous glomerulopathy) is one of the many glomerular diseases causing nephrotic syndrome. The literature indicates that autophagy is associated with the homeostasis of podocytes in glomeruli. Curcumin, the main active component in turmeric, has drawn attention for its effective bioactivities against chronic kidney disease. The current study was aimed at assessing the effects of curcumin and exploring the underlying mechanism that mediates autophagy in an animal model of passive Heymann nephritis (PHN) in rats. Passive Heymann nephritis (PHN) was induced in male SD rats by intraperitoneal injection of anti-Fx1A serum. The rats were divided into 3 groups: control (n = 10, normal diet), model group (n = 10, 0.5% sodium carboxymethylcellulose), and curcumin (n = 10, 300 mg/kg/d). The kidney function and oxidative stress indicators were measured using commercial diagnostic kits, and the histomorphology of renal tissues was observed. The number of podocytes was measured by immunohistochemistry. Meanwhile, the autophagosomes in podocyte were analyzed by transmission electron microscopy and the immunofluorescence assay pointing to p62, an autophagic marker. Western blot analyzed the levels of apoptosis, autophagy, PI3K/AKT/mTOR, and Nrf2/HO-1 pathway-associated proteins. The total cholesterol (TC), triglycerides (TG), creatinine (Scr), blood urea nitrogen (BUN), urine volume, and urine albumin of PHN rats were significantly reduced by the administration of curcumin and attenuated renal histomorphological changes in model rats. Meanwhile, curcumin improved the oxidative stress response by decreasing MDA and increasing SOD, GSH, and CAT levels in the kidney of PHN rats. Furthermore, curcumin significantly ameliorated the podocyte loss, along with the fusion, and increased the autophagic vacuoles compared to the PHN control rats. In addition, curcumin downregulated the expression of Bax, Caspase-3, p62, PI3K, p-AKT, and p-mTOR proteins and upregulated the Bcl-2, beclin1, LC3, Nrf2, and HO-1 levels in this animal model. The results provide a scientific basis that curcumin could significantly alleviate the development of MN by inducing autophagy and alleviating renal oxidative stress through the PI3K/AKT/mTOR and Nrf2/HO-1 pathways.

Diagnostic accuracy of anti-phospholipase A2 receptor (PLA2R) antibodies in idiopathic membranous nephropathy: an Italian experience

Background

Autoantibodies against-phospholipase A2 receptor (PLA2R) are specific markers of idiopathic membranous nephropathy (iMN). Enzyme-linked immunosorbent assay (ELISA) is becoming the preferred method in many laboratories for the determination of anti-PLA2R antibodies, because it provides quantitative results, and is not prone to subjective interpretation, as is the case with indirect immunofluorescence assay.

Methods

The purpose of our study was to determine the diagnostic performance of serum PLA2R antibodies detected by commercially available ELISA in a large Italian multicenter cohort of patients with biopsy-proven iMN and in patients with other renal diseases, with special focus on evaluating the optimal cut-off value to discriminate positive and negative results. A total of 495 consecutive patients were recruited. Renal biopsies were performed in all patients, and blood samples were taken before the initiation of immunosuppressive treatment.

Results

According to the clinical diagnosis and to kidney biopsy, 126 patients were diagnosed with iMN and 369 had other non-membranous nephropathies. Anti-PLA2R autoantibodies were detected using a commercial anti-PLA2R ELISA. At a cut-off value of 20 relative units (RU)/ml indicated by the manufacturer for positive classification, sensitivity was 61.1% and specificity 99.7%. At a cut-off value of 14 RU/ml indicated by the manufacturer for borderline results, sensitivity was 63.5% and specificity remained the same (99.7%). At a cut-off of 2.7 RU/ml, selected as the optimal cut-off on the basis of ROC curve analysis, sensitivity was 83.3% and specificity 95.1%. The best overall efficiency of the test was observed at 2.7 RU/ml; however, the highest positive likelihood ratio and diagnostic odds ratio were achieved at 14 RU/ml. A cut-off threshold higher than 14 RU/ml or lower than 2.7 RU/ml entailed worse test performance.

Conclusion

Depending on the clinical use (early diagnosis or as a support to confirm clinical diagnosis), nephrologists may take advantage of this evidence by choosing the most convenient cut-off. However, renal biopsy remains mandatory for the definitive diagnosis of iMN and for the assessment of disease severity.

Expression Levels of miR-30c and miR-186 in Adult Patients with Membranous Glomerulonephritis and Focal Segmental Glomerulosclerosis

Background

Nephrotic syndrome is a common renal problem with different histopathogenesis. MicroRNAs are reported to be involved in the pathophysiology of the syndrome. The aim of this study was to study the levels of miR-30c and miR-186 in NS patients.

Methods

Sixty patients with primary NS (membranous glomerulonephritis (MGN, N=30) and focal segmental glomerulosclerosis (FSGS, N=30)) and 24 healthy volunteers were included. Expression levels of the miR-30c and miR-186 were evaluated in plasma and peripheral blood mononuclear cell (PBMC) samples of adult patients with NS using real-time PCR. Moreover, an in-silico analysis was performed to understand the signaling pathways and biological procedures that may be regulated by these miRNAs.

Results

In the MGN group, significantly elevated levels of miR-30c and miR-186 were observed in PBMC (P= 0.037) and plasma (P= 0.035) samples, respectively. Moreover, there was a significant increase in miR-30c levels in PBMC samples of the FSGS group when compared to healthy controls (P= 0.004). In ROC curve analysis, combined levels of the studied miRNAs could discriminate cases from controls in plasma and blood cells (AUC≥0.72, P<0.05).

Conclusion

A panel of miRNAs may be potential biomarkers in plasma and PBMCs samples of NS patients with different subclasses. More investigations are needed with a large sample size to validate the diagnostic values of the reported miRNAs.

Renal hypoplasia can be the cause of membranous nephropathy-like lesions

BACKGROUND

Renal hypoplasia (RH) is the most common cause of chronic kidney disease in children. In cases of RH, proteinuria is often induced by glomerular hypertrophy and hyperfiltration that is commonly associated with focal segmental glomerulosclerosis. This study reports the first case series of a possible association between RH and membranous nephropathy (MN).

METHODS

Of the 168 children with RH who visited our department between 1999 and 2017, five with overt proteinuria (≥ 1 g/gCr) underwent renal biopsy. We retrospectively reviewed the medical charts and analyzed biopsy specimens using light microscopy (LM), immunofluorescence (IF), and electron microscopy.

RESULTS

The five children (four boys and one girl) had a median age of 5.5 years at the time of renal biopsy. The median proteinuria was 4.23 g/gCr (range 1.46-14.25), median serum albumin, 2.9 g/dL (range 2.3-3.7), and median estimated glomerular filtration rate, 59.7 mL/min/1.73 m² (range 36.7-103.6). LM showed segmental spike formation and mesangial hypercellularity and IF study showed segmental granular immunoglobulin G (IgG) staining (IgG1 and IgG3 dominant) along the capillary loops in all five patients. Electron-dense deposits were observed in the subepithelial and mesangial areas. Thus, the pathological studies showed MN-like lesions in all patients.

CONCLUSION

Our study suggests that RH can be the cause of MN-like lesions.

Clinicopathological features and prognosis in patients with idiopathic membranous nephropathy with hypertension

The present study analyzed the clinicopathological features and prognosis in patients with idiopathic membranous nephropathy (IMN) with hypertension. In the hypertension group, significant differences were found in the age, hypertension history, systolic blood pressure, diastolic blood pressure (DBP), mean arterial pressure, albumin, serum creatinine, low-density lipoprotein, 24 h urine protein levels, calculated estimated glomerular filtration rate (e-GFR), glomerular sclerosis, segmental sclerosis, ischemic sclerosis, interstitial fibrosis, tubular atrophy and vascular lesion compared with the non-hypertension group (P<0.05). The average follow-up time was 35.70 months (5.10-103.77 months). In total, 54 patients reported a 50% decline in e-GFR, eight patients reported progression of disease to end-stage renal disease (ESRD) and nine cases of mortality were reported. Survival analysis results suggested that patients with hypertension had a lower cumulative renal survival rate than those without hypertension (P=0.034). Multivariate Cox hazards regression analysis results suggested that DBP [hazard ratio (H), 5.160; CI, 0.865-0.989; P=0.023], age (H, 4.839; CI, 1.008-1.142; P=0.028), sex (H, 5.680; CI, 0.031-0.714; P=0.017), serum creatinine (H, 20.920; CI, 1.035-1.089; P<0.001), uric acid (H, 4.783; CI, 0.982-0.0.999; P=0.029), 24 h urine protein (H, 6.318; CI, 1.079-1.850; P=0.012), e-GFR (H, 4.008; CI, 1.001-1.062; P=0.045) and glomerular sclerosis (H, 8.722; CI, 1.860-21.559; P=0.003), segmental sclerosis (H, 7.737; CI, 7.770-13.219; P=0.005), percentage of ischemic sclerosis (H, 4.729; CI, 1.444-11.945; P=0.030), crescents (H, 5.938; CI, 0.003-0.526; P=0.015), interstitial fibrosis and tubular atrophy (H, 8.128; CI, 0.005-1.052; P=0.043), and vascular lesion (H, 4.049; CI, 1.030-9.766; P=0.044) were risk factors for the development of IMN into ESRD. The results suggested that DBP may be an independent risk factor for the development of IMN with hypertension.

Triptolide ameliorates fine particulate matter-induced podocytes injury via regulating NF-κB signaling pathway

BACKGROUND

PM2.5 is associated closely with an increased risk of membranous nephropathy (MN), however, whether PM2.5 could induce podocytes injury, the underlying pathology for MN, has not be thoroughly studied. Triptolide, an active component in Tripterygium wilfordii Hook F, is frequently used to treat MN in China, but its effects on PM2.5-induced podocytes injury is still largely unknown. Therefore, we evaluated the effects of PM2.5 on podocytes, and explored whether triptolide could improve PM2.5-induced podocytes injury and the possible underlying mechanisms.

RESULTS

Podocytes were incubated with PM2.5 after being pre-treated with triptolide, viability, apoptosis rate and migratory capacity of podocytes were determined by CCK-8 assay, flow cytometry and Transwell assay, respectively. Additionally, the levels of lactate dehydrogenase (LDH), malondialdehyde (MDA), and superoxide dismutase (SOD) in podocytes, the cytoskeleton of podocytes, the protein expressions of nephrin, podocin, Bcl-2, Bax, nuclear factor kappa-B/p65 (NF-κB/p65) and phospho-inhibitor of NF-κB (p-IκBα) were measured. Our data showed that PM2.5 treatment significantly increased the disorganization of F-actin stress fibers, the damaged structural integrity of nucleus, the deranged and dissociated cytoskeleton in podocytes, increased the podocytes apoptosis rate, the levels of MDA and LDH, markedly up-regulated the protein expression of Bax, NF-κB/p65 and p-IκBα, down-regulated the protein expression of nephrin, podocin and Bcl-2, and significantly decreased the level of SOD, the migration rate and the viability of podocytes, compared with those of the untreated podocytes. These effects of PM2.5 on podocytes, however, were reversed by triptolide administration.

CONCLUSION

These results suggest that triptolide could prevent against PM2.5-induced podocytes injury via suppressing NF-κB signaling pathway.

Proteomic Analysis of Complement Proteins in Membranous Nephropathy

Introduction

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in Caucasian adults. Phospholipase A2 receptor (PLA2R)– and exostosin 1 (EXT1)/exostosin 2 (EXT2)–associated MN represent the most common primary and secondary forms of MN. The complement profile using a proteomics approach has not been studied in these 2 common forms of MN.

Methods

We used laser microdissection and mass spectrometry (MS/MS) to dissect glomeruli and identify glomerular complement proteins in PLA2R-associated (n = 7), EXT1/EXT2-associated MN (n = 21), and 11 control cases (time 0 transplant biopsies).

Results

MS/MS identified high total spectral counts for PLA2R and EXT1/EXT2 in corresponding cases of PLA2R- and EXT1/EXT2-positive MN. Both PLA2R- and EXT1/EXT2-associated MN had high spectral counts of complement proteins C3, C4, C5, C6, C7, C8, and C9. Complement protein C1 was present in low spectral counts in EXT1/EXT2-associated MN. Regulators of complement activation that were detected in MN included higher spectral counts of FH, FHR-1, FHR-5, clusterin, vitronectin and lower spectral counts of FHR-3, FHR-4, and CD59. Low spectral counts of FB and properdin, key components of the alternative pathway, also were detected. IgG4 and IgG1 were the most abundant IgG subclasses in PLA2R- and EXT1/EXT2-associated MN. Lower spectral counts for C3, C4, and C5 were detected in control cases when compared with MN.

Conclusion

Significant complement activation is present in MN as evidenced by large spectral counts of complement proteins from C3- and C4-based pathways, including regulatory proteins of complement pathways. These data suggest that anticomplement drugs may be effective in treatment for MN.

Involvement of prohibitin 1 and prohibitin 2 upregulation in cBSA-induced podocyte cytotoxicity

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults, when not effectively treated. The aim of this study was to discover new targets for the diagnosis and treatment of MN. A reliable mouse model of MN was used by the administration of cationic bovine serum albumin (cBSA). Mice with MN exhibited proteinuria, histopathological changes, and accumulation of immune complexes in the glomerular basement membrane. Label-free proteomics analysis was performed to identify changes in protein expression, and the overexpressed proteins were evaluated. There were 273 proteins that showed significantly different expression in mice with MN, as compared to the controls. String analysis showed that functions related to cellular catabolic processes were downregulated in MN. Among the differentially expressed proteins, prohibitin 1 (PHB1) and prohibitin 2 (PHB2) were upregulated in the kidneys of mice with MN, as demonstrated by immunohistochemistry (IHC), and this upregulation was observed in both the tubular cells and glomeruli. Both shRNA-mediated knockdown of PHB1 or PHB2 inhibited tumor suppressor p53 expression and significantly promoted podocyte proliferation. In addition, both PHB1 and PHB2 were responsible for cBSA-induced cytotoxicity. Microarray analysis further revealed that the upregulation of PHB1 and PHB2 may be due to a blockage of proteasome activity. These data demonstrate that the upregulation of PHB2 is involved in cBSA-mediated podocyte cytotoxicity, which may lead to MN development.

Chronic kidney disease: a review of proteomic and metabolomic approaches to membranous glomerulonephritis, focal segmental glomerulosclerosis, and IgA nephropathy biomarkers

Chronic Kidney Disease (CKD) is a global health problem annually affecting millions of people around the world. It is a comprehensive syndrome, and various factors may contribute to its occurrence. In this study, it was attempted to provide an accurate definition of chronic kidney disease; followed by focusing and discussing on molecular pathogenesis, novel diagnosis approaches based on biomarkers, recent effective antigens and new therapeutic procedures related to high-risk chronic kidney disease such as membranous glomerulonephritis, focal segmental glomerulosclerosis, and IgA nephropathy, which may lead to end-stage renal diseases. Additionally, a considerable number of metabolites and proteins that have previously been discovered and recommended as potential biomarkers of various CKD_s using ‘-omics-’ technologies, proteomics, and metabolomics were reviewed.

Comprehensive expression profiles and bioinformatics analysis reveal special circular RNA expression and potential predictability in the peripheral blood of humans with idiopathic membranous nephropathy

The etiology of idiopathic membranous nephropathy (IMN) is considered to be closely associated with immunoregulation and genetic factors. Circular RNAs (circRNAs) have been found to regulate gene expression in various organisms, and to play an important role in multiple physiological and pathological processes, which may be involved in the pathogenesis of IMN. The purpose of the present study was to investigate the potential relationship between circRNAs in peripheral blood and disease. The diagnoses of IMN were confirmed using electron microscopy and immunofluorescence. Total RNA was isolated and microarray analysis was used to detect the expression levels of circRNAs in the peripheral blood of patients with IMN and in normal subjects. Selected genes from the microarray were selected and verified by reverse transcription‑quantitative (RT‑q)PCR. Bioinformatics tools were applied for further functional evaluation, and the potential disease predictability of circRNAs was determined using receiver‑operating characteristic (ROC) curves. The results showed that a total of 955 differentially expressed circRNAs were found in blood samples, 645 of which were upregulated and 310 which were downregulated. In total, five candidate circRNAs were validated using RT‑qPCR analysis. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses identified numerous types of target genes and their corresponding microRNAs (miRNAs). The miRNAs identified were involved in biological processes and enriched in multiple important pathways, including the mitogen‑activated protein kinase, transforming growth factor‑β and Ras signaling pathways. The levels of circ_101319 were significantly higher (P<0.001) and exhibited promising diagnostic value in patients with IMN (area under ROC =0.89). The co‑expression network constructed for circ_101319 indicated that it may be associated with membranous nephropathy‑related pathways by mediating miRNAs. In conclusion, the present study revealed the expression and functional profile of differentially expressed circRNAs in the peripheral blood of patients with IMN, and provided new perspectives to predict and elucidate the development of IMN.

A glomerulus-on-a-chip to recapitulate the human glomerular filtration barrier

In this work we model the glomerular filtration barrier, the structure responsible for filtering the blood and preventing the loss of proteins, using human podocytes and glomerular endothelial cells seeded into microfluidic chips. In long-term cultures, cells maintain their morphology, form capillary-like structures and express slit diaphragm proteins. This system recapitulates functions and structure of the glomerulus, including permselectivity. When exposed to sera from patients with anti-podocyte autoantibodies, the chips show albuminuria proportional to patients' proteinuria, phenomenon not observed with sera from healthy controls or individuals with primary podocyte defects. We also show its applicability for renal disease modeling and drug testing. A total of 2000 independent chips were analyzed, supporting high reproducibility and validation of the system for high-throughput screening of therapeutic compounds. The study of the patho-physiology of the glomerulus and identification of therapeutic targets are also feasible using this chip.

Lipid metabolism participates in human membranous nephropathy identified by whole-genome gene expression profiling

A genomics approach is an effective way to understand the possible mechanisms underlying the onset and progression of disease. However, very limited results have been published regarding whole-genome expression analysis of human idiopathic membranous nephropathy (iMN) using renal tissue. In the present study, gene expression profiling using renal cortex tissue from iMN patients and healthy controls was conducted; differentially expressed genes (DEGs) were filtered out, and 167 up- and 291 down-regulated genes were identified as overlapping DEGs (ODEGs). Moreover, enrichment analysis and protein-protein network construction were performed, revealing enrichment of genes mainly in cholesterol metabolism and arachidonic acid metabolism, among others, with 38 hub genes obtained. Furthermore, we found several associations between circulating lipid concentrations and hub gene signal intensities in the renal cortex. Our findings indicate that lipid metabolism, including cholesterol metabolism and arachidonic acid metabolism, may participate in iMN pathogenesis through key genes, including apolipoprotein A1 (APOA1), apolipoprotein B (APOB), apolipoprotein C3 (APOC3), cholesteryl ester transfer protein (CETP), and phospholipase A2 group XIIB (PLA2G12B).

Exostosin 1/Exostosin 2-Associated Membranous Nephropathy

BACKGROUND

In membranous nephropathy (MN), which is characterized by deposition of immune complexes along the glomerular basement membrane (GBM), phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain-containing 7A are target antigens in approximately 70% and 1%-5% of cases of primary MN, respectively. In other cases of primary MN and in secondary MN, the target antigens are unknown.

METHODS

We studied 224 cases of biopsy-proven PLA2R-negative MN and 102 controls (including 47 cases of PLA2R-associated MN) in pilot and discovery cohorts. We also evaluated 48 cases of PLA2R-negative presumed primary MN and lupus MN in a validation cohort. We used laser microdissection and mass spectrometry to identify new antigens, which were localized by immunohistochemistry.

RESULTS

Mass spectrometry detected exostosin 1 (EXT1) and exostosin 2 (EXT2) in 21 cases of PLA2R-negative MN, but not in PLA2R-associated MN and control cases. Immunohistochemistry staining revealed bright granular GBM staining for EXT1 and EXT2. Clinical and biopsy findings showed features of autoimmune disease, including lupus, in 80.7% of the 26 EXT1/EXT2-associated MN cases we identified. In the validation cohort, we confirmed that EXT1/EXT2 staining was detected in pure class 5 lupus nephritis (eight of 18 patients) and in presumed primary MN associated with signs of autoimmunity (three of 16 patients); only one of the 14 cases of mixed class 5 and 3/4 lupus nephritis was positive for EXT1/EXT2. Tests in seven patients with EXT1/EXT2-associated MN found no circulating anti-exostosin antibodies.

CONCLUSIONS

A subset of MN is associated with accumulation of EXT1 and EXT2 in the GBM. Autoimmune disease is common in this group of patients.